Photon Density In A Light Beam

Force Exerted By A Light Beam On A Surface

The band of coloured components of a light beam

A: In the wave picture of light, intensity of light is determined by the square of the amplitude of the wave. R: In the photon picture of light, for a given frequency, intensity of light is determined by the numberof photons per unit area.

There are N_(1) photons of frequency v_(1) , in a beam of light, In another light beam of equal energy there are N_(2) photons of frequency v_(2) . Then N_(1) and N_(2) are related as

A beam of light of wavelength lambda is totally reflected at normal incidence by a plane mirror . The intensity of the light is such that photons hit the mirror . The intensity of the light is such that photons hit the mirror at a rote n . Given that the Planck constant is h , the force exerted on the mirror by this beam is

There is a parallel beam of light of larger aperture . Let I be the intensity of light . Perfectly reflecting sphere of radius r is kept in the path of this parallel beam . Find the force exerted by the light beam on sphere .

A 100 W sodium lamp is radiating light of wavelength 5890A , uniformly in all directions, a. At what rate, photons are emitted from the lamp? b. At what distance from the lamp, the average flux is 1 photon( cm^2-s)^-1? c. What are the photon flux and photon density at 2m from the lamp?